Synthesis 2017; 49(18): 4141-4150
DOI: 10.1055/s-0036-1588438
special topic
© Georg Thieme Verlag Stuttgart · New York

C4 Pictet–Spengler Reactions for the Synthesis of Core Structures in Hyrtiazepine Alkaloids

Takumi Abe*, Tomohiro Haruyama, Koji Yamada*
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Publication History

Received: 10 March 2017

Accepted after revision: 04 May 2017

Publication Date:
07 June 2017 (eFirst)

Published as part of the Special Topic Modern Cyclization Strategies in Synthesis

Abstract

The hyrtiazepine alkaloids are a family of bisindole natural products that have the azepinoindole backbone. We developed a biomimetic approach by constructing the azepinoindole core in a one-pot manner through 1,4-diazabicyclo[2.2.2]octane/2,2,2-trifluoroethanol (DABCO/TFE) promoted Pictet–Spengler reaction onto the C-4 position of tryptophan. This strategy allowed the synthesis of common key structures of these families. The key intermediate can be converted into the 3H-pyrano[2,3-b:5,6-e′]diindol intermediate present in hyrtimomines A and B, as well as the azepinoindole core present in fargesine.

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